If $x \bigtriangleup y = 2x^{2}+y^{2}$ and $x \diamond y = x+7y$, find $(-1 \bigtriangleup -4) \diamond -3$.
Answer: First, find $-1 \bigtriangleup -4$ $ -1 \bigtriangleup -4 = 2(-1)^{2}+(-4)^{2}$ $ \hphantom{-1 \bigtriangleup -4} = 18$ Now, find $18 \diamond -3$ $ 18 \diamond -3 = 18+(7)(-3)$ $ \hphantom{18 \diamond -3} = -3$.